One of the methods for detecting energetic ionizing particles such as electrons or protons is by means of scintillating materials such as plastics, glasses or liquids. One particular configuration for such a detector is an array of optical fibers made of a scintillating material through which the energetic particle passes. In its passage, it causes some of its energy to be converted to light by the scintillating substance, and this light is transmitted along the fiber or fibers by internal reflection to the end face where it is detected by means of various electro-optical devices.
One specific form of scintillating detector consists of an array of parallel minute glass tubes which are filled with a scintillating liquid and suitably sealed at the ends. Such arrays (termed parallel arrays) may contain several thousand or tens of thousands of minute capillaries ranging in size from 5 to 100 microns.
In current detector arrays, these capillaries are made by glass drawing processes leading to an accurately aligned, parallel array. Such an array may be as much as one meter or longer in length. An energetic particle traversing this array will leave a "track" consisting of light generated in a series of capillary "fibers" along this track. The track will be seen as a series of dots by the electro-optical readout system. This is shown schematically as a line in FIG. 1. In this Figure a set 2 of six scintillating capillary arrays 21, each array comprising a group of minute capillaries, are placed in a line as shown on the right side of FIG. 1 (four array 21 are shown enlarged on the right). An energetic ionizing particle 1 traversing each array of capillaries will cause a track 31 to be seen as a series of dots (shown schematically as a line) as the individual capillaries emit light. For parallel capillaries in a given array, the track will be straight with no rotated track segments.
Further background information on the prior art over which the present invention is an improvement is disclosed and described in two technical articles, one by V. Zacek, "Szintillierende Mikrolichtleiter zum Hochauflosenden Teilchennachweis", Physikalische Blatter 47, (1991) 837-839; and the other by A. Artomonov, et al, "Investigations On Capillaries Filled With Liquid Scintillator For High Resolution Particle Tracking", Nuclear Instruments and Methods A300, (1991) 53-62.
In a parallel array of capillaries, the track of any beam of particles will appear the same at the end face of the array independent of the point along the length of the array where it entered. There is a loss of light along the array due to attenuation, but this may not be recognizable as a means for determining the point of entry along the length.
While the invention will be described with respect to an array of minute capillaries it is entirely within the spirit and scope of the invention that the array be composed of scintillating optical fibers of plastic or glass as well as capillaries filled with a scintillating liquid.
Therefore, for purposes of claiming the invention the language "optical fibers" is intended to include scintillating optical fibers of glass or plastic including minute sealed capillaries filled with a scintillating liquid.